1. Field of Invention
This invention is directed to apparatus and methods of controlling image forming apparatus, and in particular to the use of tone reproduction curves (TRC) in the control of image forming apparatus.
2. Description of Related Art
A typical image forming apparatus includes an input device, such as, for example, a scanner. The input device inputs image information relating to an original image into the apparatus. The typical image forming apparatus also includes an output device that forms an image based on the input image information. The output device can form an image in any medium, such as, for example, a printer that prints an image on a recording medium, or a monitor that displays an image on a screen.
However, discrepancies typically exist between the image information input by the input device and the image formed by the output device. These discrepancies can take the form of differences in contrast and brightness between the input image information and the output image. Such differences ultimately prevent the output image from being a true and accurate representation of the original image.
Tone reproduction curves (TRC) can be used to compensate for the differences in brightness and contrast between the input image information and output image. For example, each type of input device and output device can define a certain and unique curve based upon brightness versus contrast. Differences between these curves cause the output image to vary from the original image, as discussed above. However, a TRC can be used to compensate for the differences so as to bring the curves together and thereby enable the output image to more closely resemble the original image.
It is therefore desirable to provide an image forming apparatus with a system TRC. The system TRC can be calculated once the characteristics of the input and output devices are known, such as the devices"" unique brightness versus contrast curves. In operation, the image forming apparatus can augment the input image information via the calculated system TRC so that the output device is able to provide an output image that closely matches the original image in terms of brightness and contrast.
It is also desirable to enable a user to set the TRC to suit the user""s particular needs. For example, the TRC can be represented to the user as five bars, which the user can set to provide a customized system TRC and thereby achieve a desired response. Thus, the user can be provided with the flexibility to choose an exact input/output relationship for the document being processed. The five settings provided on sliders can be used to calculate the system TRC using linear interpolation of the points, and the resultant image processing TRC can be computed by any method, such as the Jones plotting method.
Exemplary apparatus and methods for providing the user with the flexibility discussed above via graphical user interfaces and image capturing devices are disclosed in co-pending U.S. patent application Ser. No. 09/487,271, filed Jan. 19, 2000, entitled SYSTEMS, METHODS AND GRAPHICAL USER INTERFACES FOR CONTROLLING TONE REPRODUCTION CURVES OF IMAGE CAPTURE AND FORMING DEVICES, the entire content of which is hereby incorporated into this application by reference.
It is further desirable to combine these operations so as to adjust a current system TRC with a manually adjustable five bar TRC. All permutations of settings of current system TRC""s and five bar TRC""s can be stored in the image forming apparatus prior to operation. However, storing all of these permutations requires a significant amount of storage space, which increases the cost of the image forming apparatus.
It is therefore desirable to enable the image forming apparatus to determine a new system TRC, based upon the current manually adjustable five bar TRC, in real time, which would reduce the amount of storage space required. The invention is intended to cover all methods and apparatus capable of performing the real time determinations.
For example, the current system TRC being used for the mode of processing can be cascaded with manually changeable five bar settings. The system TRC for the selected mode of processing and the five bar settings can be combined by various methods, such as by using basic look-up tables (LUT) and linear interpolation methods to create a new adjusted system TRC.
The new adjusted TRC can then be used by an image processing sub-system of the image forming apparatus to adjust the input image to produce the desired output. Such an operation can provide for finer tuning of the system TRC than what would be provided by merely providing the user with contrast and brightness adjustments, which enables the user to achieve enhanced flexibility in determining how to adjust an output image.
Thus, a method of controlling an image forming apparatus in accordance with the invention can include the steps of: providing a system tone reproduction curve; representing a manually adjustable tone reproduction curve; modifying the manually adjustable tone reproduction curve to be consistent with the system tone reproduction curve; and cascading the manually adjustable tone reproduction curve with the system tone reproduction curve to provide a new adjusted tone reproduction curve.
Further, an image forming apparatus in accordance with the invention can include: a medium that stores a system tone reproduction curve; a graphical user interface that represents a manually adjustable tone reproduction curve; and a determining device that cascades the manually adjustable tone reproduction curve with the system tone reproduction curve to provide a new adjusted tone reproduction curve.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments of the systems and methods according to this invention.